A shape inspection called “highlight test” has been commonly known as a technique to evaluate the exterior quality of a car or the like, in which the surface shape of the object to be evaluated is evaluated in three dimensions. In the highlight test, the surface shape of an object to be evaluated is inspected by the flow state of an optical beam pattern that is formed on the surface of the object to be evaluated by collimating an optical beam emitted from a light source such as a fluorescent light and radiating the collimated optical beam to the object through a slit or the like. In such a highlight test, the optical beam pattern formed on the surface of an object to be evaluated is commonly called “highlight lines”, and an inspection for projections and depressions and the roundness of the surface shape is performed on the object based on the highlight lines formed on the surface shape of the object. Specifically, an organoleptic test in which a skilled inspector makes visual confirmation and an automatic test in which an image obtained by photographing the surface of an object is compared with an ideal optical pattern have been known (for example, Patent documents 1 and 2).
When the above-described Patent documents 1 and 2 obtain the highlight lines by taking an image of an optical beam pattern formed on the surface of an object to be inspected, they quantify the highlight lines in an attempt to quantitatively evaluate the surface shape quality of the object to be inspected. Specifically, the purpose of a technique described in Patent document 1 is, when it takes image data into a computer as highlight lines, to eliminate noise contained in the taken image data and to quantitatively calculate the surface shape of the object to be inspected from the highlight line data from which noise is eliminated. Furthermore, a technique described in Patent document 2 obtains a pattern that is recognized as highlight lines from image data obtained as a result of photographing by applying the image data to a free-form curve, and the purpose of the technique is to prevent the occurrence of discontinuity problems and uniformity problems in the recognized highlight lines.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 6-194148    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 7-332950